reconnects failed

[ideazw]

use connection pool to Redis server, not used for a long time,when used again.
the connection is broken,can't reconnects.

#0 0x00007ffff7032f96 in send () from /lib64/libpthread.so.0
#1 0x00000000006ddb38 in redisNetWrite (c=) at sds.h:99
#2 0x00000000006d6b89 in redisBufferWrite (c=, done=) at hiredis.c:910
#3 0x00000000006d6d83 in redisGetReply (c=, reply=) at hiredis.c:948
#4 0x00000000005944c1 in sw::redis::Connection::recv() ()
#5 0x000000000052924a in sw::redis::Redis::_command<void ()(sw::redis::Connection&, sw::redis::StringView const&), sw::redis::StringView const&> (this=0xa4db50, connection=...,
cmd=0x5a48d0 <sw::redis::cmd::incr(sw::redis::Connection&, sw::redis::StringView const&)>) at /home/wei.zhang/projects/TingShuComment/include/sw/redis++/redis.hpp:1272
#6 0x0000000000528106 in sw::redis::Redis::command<void ()(sw::redis::Connection&, sw::redis::StringView const&), sw::redis::StringView const&> (this=0xa4db50,
cmd=0x5a48d0 <sw::redis::cmd::incr(sw::redis::Connection&, sw::redis::StringView const&)>) at /home/wei.zhang/projects/TingShuComment/include/sw/redis++/redis.hpp:48
#7 0x000000000059bc7f in sw::redis::Redis::incr(sw::redis::StringView const&) ()